Valve operating apparatus and method for an engine

ABSTRACT

A valve operating apparatus for an internal combustion engine including: a housing ( 2 ); a reciprocating piston ( 1 ) residing wholly within the housing ( 2 ), the reciprocating piston ( 1 ) driving one or more poppet valves ( 7 ); a first fluid supply path and a first fluid drain path, each path being controllable to supply or drain fluid to/from a first reciprocating piston end ( 16 ); a second fluid supply path and a second fluid drain path, each path being controllable to supply or drain fluid to/from a second reciprocating piston end ( 17 ); wherein said reciprocating piston ( 1 ), in use, is driven between a first position and a second position by controlling said fluid in said supply and drain paths, thereby operating said one or more poppet valves ( 7 ), and wherein a connector ( 9 ) passes through an aperture ( 14 ) in said housing ( 2 ) to connect said reciprocating piston ( 1 ) to said one or more poppet valves ( 7 ), said reciprocating piston ( 1 ) in co-operation with an internal wall of the housing forming a seal to prevent substantial egress of fluid from the housing ( 2 ) through said aperture ( 14 ).

FIELD OF THE INVENTION

The present invention relates to a means and method of operating theintake and/or exhaust valves of an internal combustion engine. Moreparticularly the invention relates to a connection arrangement betweenthe operating apparatus and the valves, and the use of pressurised fluidto actuate valves during operation of an engine.

BACKGROUND OF THE INVENTION

Controlling the lift and timing of intake and/or exhaust (poppet) valvesin an automotive engine is a necessary aspect of operating an engine.Traditionally, control has been achieved by mechanical systems using acam to drive the stem of the intake or exhaust poppet valves, while athrottle was used to control the air flow supplied to individualcylinders. More recently, it has been known to have a cam which allowsthe poppet valve lift to be adjusted. However, either approach resultsin efficiency losses.

Many solutions have been proposed to address the efficiency lossproblem. For example, mechanical solutions have been proposed to shiftthe phase of the camshaft or the lift of the poppet valves to improveefficiency. There have also been hydraulic-mechanical proposalsattempting to shift the phase of the camshaft or lift of the valves.These systems tend to be very complicated and are not economic tomanufacture.

Electro-magnetic solutions using a solenoid to drive the poppet valveshave also been proposed, however a solenoid of sufficient size isrelatively big, heavy and expensive, and thus not suitable for massproduction.

Hydraulic solutions without a camshaft have been proposed, however thecomplexity of previous attempts to replace a valve train cam andthrottle with a hydraulic solution has made them difficult tomanufacture and thus uneconomic. The previously proposed hydraulicallydriven poppet valves generally include both a high and a low pressurefluid supply, requiring major modifications to an existing engine usinga camshaft.

Hence, the retrofitting of such devices is expensive because prior artproposals require the hydraulic system to be mounted in-line with thelongitudinal axis of the poppet valve and as a result, the existingcylinder head requires extensive modification. Such solutions aregenerally considered to only be suitable for incorporating into purposebuilt engines.

Some prior solutions tend to rely on a surface area difference at eachend of the actuating piston, actuating the valve in one direction by theresulting force of a surface area difference. By supplying fluidconstantly to a first end of the piston and alternately supplying anddraining fluid to the second end, the fluid pressure at the first end,having smaller surface area, causes the piston to move when there is nopressure at the second end, and the fluid pressure multiplied by alarger surface area at the second end results in a greater force toreturn the piston when fluid is supplied to the second end. Accordingly,the solution involving differing surface areas remains inefficient, asthe force applied by the pressure at the larger end must overcome theconstant force applied by the pressure at the smaller end, slowing downthe system and causing difficulty in operating at the high speedsrequired for a combustion engine.

For example, DE19826047A1 and WO03106820A1 disclose hydraulic actuationof the poppet valve by supplying fluid to a reciprocating piston at anominally constant pressure. The force driving the piston, which may beapproximated as Force=Pressure×Area, is dependent on the difference insurface area of each end of the piston. Actuation methods based uponthis principle of operation necessarily face difficulty in reaching thehigh operating speeds required by an internal combustion engine.

Other prior solutions rely on constantly supplying fluid at a lowerpressure to one piston end, and supplying fluid at a higher pressure tothe other end to drive the piston. By alternately supplying and drainingthe higher pressure end of the piston, the piston is caused toreciprocate. However, this again results in slowing down the system andcausing difficulty in operating at the high speeds required for acombustion engine.

Further efficiency problems exist in the above systems and in theelectro-hydraulic valve operating apparatus systems disclosed inDE19826047A1, WO9207172 and U.S. Pat. No. 6,321,703. Problemsexperienced by such electro-hydraulic valve operating apparatus includethe difficulty of sealing fast moving parts, in particular the poppetvalves themselves. Where a valve stem passes through the wall of achamber that is required to contain fluid under pressure, a sealextending around the stem is necessarily required to prevent asignificant leakage of fluid from the chamber around the valve stem.Accordingly, the stem requires a “high pressure” seal extending aroundthe stem to prevent loss of fluid. Of course, a high pressure sealcauses a significant frictional force that must be overcome in order tooperate the valve, hence requiring higher fluid pressures in the valveoperating apparatus in order to operate the piston. This in turnrequires a stronger seal to prevent pressurised fluid from leaking outof a chamber around the poppet valve stem. The frictional forcepresented by a high pressure seal and the greater fluid pressurerequired to operate the valve results in less precision of control ofthe position of the poppet valve(s), less ability to provide variablecontrol and hence lower overall engine efficiency, as the lift andtiming of the poppet valves, the amounts of air being fed into theengine and hence thermodynamic efficiency of the engine cannot becontrolled with the desired precision.

The prior art does not provide a simple, reliable and in particular,efficient, variable engine valve control system. Previously proposedsolutions are complex and inefficient to operate. The inefficiencies offluid pressures working against each other and the internal frictioncaused by high pressure seals around valve stems result in lessprecision of control and difficulties in achieving operation at highspeed. Ultimately, the inability to operate the engine in the mostefficient way inhibits the ability to operate a hydraulic valveactuating apparatus at the speeds required. The prior art is also notgenerally suitable for retrofitting to existing engines that include acamshaft.

As the characteristics of simplicity, reliability and efficiency areimportant attributes for components of complex machines such as engines,it is a primary object of the present invention to provide a means andmethod of operating valves that embodies one or more of thesecharacteristics moreso than devices proposed in the prior art.

Any discussion of documents, devices, acts or knowledge in thisspecification is included to explain the context of the invention. Itshould not be taken as an admission that any of the material formed partof the prior art base or the common general knowledge in the relevantart on or before the priority date of the claims herein.

SUMMARY OF THE INVENTION

A first aspect of the present invention provides a valve operatingapparatus for an internal combustion engine including:

a housing;

a reciprocating piston residing wholly within the housing, thereciprocating piston driving one or more poppet valves;

a first fluid supply path and a first fluid drain path, each path beingcontrollable to supply or drain fluid to/from a first reciprocatingpiston end;

a second fluid supply path and a second fluid drain path, each pathbeing controllable to supply or drain fluid to/from a secondreciprocating piston end;

wherein said reciprocating piston, in use, is driven between a firstposition and a second position by controlling said fluid in said supplyand drain paths, thereby operating said one or more poppet valves, andwherein a connector passes through an aperture in said housing toconnect said reciprocating piston to said one or more poppet valves,said reciprocating piston in co-operation with an internal wall of thehousing forming a seal to prevent substantial egress of fluid from thehousing through said aperture.

In a particularly preferred embodiment, said aperture is substantiallysealed by at least a portion of the external surface of saidreciprocating piston to prevent egress of fluid from the housing throughsaid aperture.

Prior hydraulic valve operating apparatus requires a seal between themoving poppet valve stem and the hydraulic fluid supply at the pointwhere the poppet valve stem passes through the housing. Advantageously,the present arrangement avoids such a seal. Instead, the reciprocatingpiston itself acts as a seal to prevent pressurised fluid from reachingthe aperture from within the housing.

Internal friction in the hydraulic valve operating apparatus is lowered,as friction between the reciprocating piston and housing, alreadypresent, is not significantly increased when the reciprocating piston isused to prevent leakage of fluid through an aperture in an external wallof the housing.

In addition to reducing the number of parts required, the valveoperating apparatus of the present invention operates more efficiently,with less friction as compared with prior systems. Accordingly, higherengine operating speeds may be reached as a result of the increasedefficiency of operation. Furthermore, the lower internal friction meansthat the hydraulic system may operate at a lower fluid pressure toeffect actuation of the poppet valves.

In a particularly preferred embodiment of the invention a connector rodis fixed to the reciprocating piston and connects to one or more poppetvalves. The connector rod may be integrally formed with the piston, orcould be a rod passing through a hole in the piston, and hence caused tomove longitudinally with the piston as the piston reciprocates. Theconnector preferably passes through two apertures in the housing, one oneach side of the piston, in order to drive two poppet valves, however anembodiment where the connector passes through a single aperture isenvisaged.

In a preferred embodiment of the present invention, said firstreciprocating piston end and said second reciprocating piston end havesubstantially the same surface area, movement of the reciprocatingpiston being due to the alternating supply and drainage of fluid to thepiston ends. This preferred embodiment of the present invention relieson a pressure difference as the driving force in both operatingdirections and preferably fluid at the same nominal pressure is suppliedin turn to each end of the reciprocating piston.

Although the pressures at each end of the reciprocating piston may workagainst each other when it is desirable to control the reciprocatingpiston, for example, to decelerate, in general the force (pressure)applied at one end of the reciprocating piston does not have to overcomean opposing force at the other end, that in prior systems is caused bythe constant supply of fluid to one end of the piston. In prior systems,work and thus a higher pressure are required to overcome the forceexerted by this fluid when the piston is to be driven against theconstant pressure. Nonetheless, in a less preferred embodiment of theinvention there is a difference in pressure between fluid delivered tothe first reciprocating piston end and fluid delivered to the secondreciprocating piston end.

Another embodiment of the present invention relies upon a constantsupply of fluid being supplied to one reciprocating piston end, thepiston ends being of differing surface areas so that alternating supplyof fluid to the other piston end will cause the piston to reciprocate.Again, this embodiment is less preferred as overall efficiency will belowered.

In yet another preferred embodiment of the present invention, said fluidsupply and drain paths are opened and closed to control the flow of saidfluid, said opening or closing of each said fluid supply and drain pathsachieved by one or more solenoid valves or rotary valves, or acombination of said control valve types. These fast reacting controlvalves enhance the responsiveness of an apparatus according to thepresent invention.

In a particularly preferred embodiment of the present invention, each ofsaid first fluid supply path, first fluid drain path, second fluidsupply path and second fluid drain path has a control valve, operationof the four said control valves regulating the flow of fluid to saidfirst and second reciprocating piston ends, thus enabling control of themovement of the reciprocating piston and hence operation of the on ormore poppet valves.

Preferably, each of the four said control valves is independentlyoperable. Preferably, each of the four said control valves may beoperable to have a closed, partially open or open state.

The four control valves, one for each of the supply and drain paths,allow an extensive control of the movement of the reciprocating pistonand hence the poppet valves, including the ability to operate thereciprocating piston and poppet valves at high speeds and to accelerateand decelerate the reciprocating piston to prevent valve crash or meetother valve timing objectives.

Another preferred embodiment of the invention has a reservoir of highpressure fluid in fluid connection with one or more of said fluid supplypaths. Use of a reservoir may be of assistance at engine start up, inorder that the engine may be started without difficulty as there is notime delay to build up pressure, as may occur when a pump alone is used.Furthermore, any momentary interruption of supply from the pressuresupply device may be compensated for by the high pressure reservoir.

Controlling said fluid in said supply and drain paths may be achievedvia an engine management system, also referred to as an electroniccontrol device. Information regarding the engine speed, desired torqueoutput, fluid and air temperatures and pressures, air humidity and inletair mass flow and valve positions may be provided to the enginemanagement system controller. The engine management system controllermay enable variable lift and variable timing control of the one or morepoppet valves.

In a preferred embodiment, the reciprocating piston may be deceleratedby controlling said fluid in said supply and drain paths to avoidcrashing of said one or more poppet valves onto their respective seats.

In another preferred embodiment, the reciprocating piston is biased to apredetermined position when in an inoperative state, thereby biasingeach said poppet valve to a predetermined position. The biasing meansmay be prevented from acting on the reciprocating piston when thereciprocating piston is in an operative state.

For example, biasing means such as a spring may be provided. To ensureextra work by the hydraulic system is not required to overcome any forceexerted by such a spring, the spring could optionally be snibbed inplace in a compressed state while the engine is in operation, only beingunsnibbed when the engine is inoperative, in order to bias thereciprocating piston and poppet valve(s) to a known position.

Further, the reciprocating piston may be partially hollow, thusproviding a surface upon which vertical force may act at least at oneend of said reciprocating piston.

In an above described embodiment, the connection between thereciprocating piston and the one or more poppet valves is effected by aconnector rod fixed to the reciprocating piston. Preferably, the or eachconnection to the one or more poppet valves allows the one or morepoppet valves to spin about their respective longitudinal axes.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described, withoutlimiting the overall scope of the invention, with reference to theaccompanying drawings in which:

FIG. 1 shows a schematic of one embodiment of the present invention; and

FIG. 1 a shows a schematic of a second embodiment of the presentinvention; and

FIG. 2 shows a cross-sectional view of a preferred embodiment of thepresent invention; and

FIG. 3 shows a cross-sectional view rotated 90 degrees of the embodimentof FIG. 2; and

FIG. 4 shows an embodiment of a solenoid valve; and

FIG. 5 shows yet another preferred embodiment of the present invention;and

FIG. 6 shows a cross-sectional view of another embodiment of the presentinvention.

FIG. 7 shows a cross-sectional view rotated 90 degrees of the embodimentof FIG. 6.

DESCRIPTION OF PREFERRED EMBODIMENT

In a preferred embodiment of the invention, a valve operating apparatus31 (also referred to herein as a valve train device) forms part of ahydraulic system. Alternative embodiments of the hydraulic system areshown schematically in FIGS. 1 and 1 a, while a more detailedrepresentation of a preferred embodiment of the invention is shown inFIG. 5.

Referring to FIGS. 1, 1 a and 5, a pressure supply device 20, forexample a pump driven by the engine, delivers pressurised fluid from asump 21 at low pressure to a high pressure reservoir 22. When the highpressure reservoir 22 is full, a pressure relief valve 23 (also referredto herein as a pressure control valve) located between the pressuresupply device 20 and the high pressure reservoir 22 drains any excessfluid back to the sump 21. It should, however, be noted that a highpressure reservoir 22, while preferred, is not essential to the presentinvention. Furthermore, the high pressure distributor 29 schematicallyshown in FIG. 1 may be provided as a part of the flow control valve 30of FIG. 2, or as a part of the valve operating apparatus 31 or valvetrain device itself. It should also be noted that a single hydraulicsystem could operate a number of valve operating apparatus 31 or valvetrain devices.

Referring now to FIGS. 2 and 3, or alternately to FIGS. 6 and 7, whichshow preferred embodiments of a valve operating apparatus 31 for aninternal combustion engine, a simplified method of operation of theapparatus is as follows. Fluid at pressure may be supplied from eitherthe high pressure reservoir 22 or from the pressure supply device 20,via a first fluid supply path 3, to a first chamber 11 formed between afirst end 16 of the reciprocating piston 1 and housing 2. A first fluiddrain path 5 connecting said first chamber 11 to a low pressurereservoir or sump 21 is closed and the pressure thereby built up in thefirst chamber 11 causes the reciprocating piston 1 to be hydraulicallydriven from a first position to a second position. At the same time, thesecond fluid supply path 4 is closed and the second fluid drain path 6is open, allowing any fluid in the second chamber 10 to drain throughthe second drain path 6 to the sump 21. Motion of the reciprocatingpiston 1 assists this draining.

The reciprocating piston is then returned from the second position tothe first position by a similar process, in which fluid at pressure issupplied from the high pressure reservoir 22 or from the pressure supplydevice 20, via a second fluid supply path 4, to a second chamber 10formed between a second end 17 of the reciprocating piston 1 and housing2. A first fluid drain path 6 connecting said second chamber 10 to thesump 21 is closed and the pressure thereby built up in the secondchamber 10 causes the reciprocating piston 1 to be hydraulically drivenfrom the second position to the first position. At the same time, thefirst fluid supply path 3 is closed and the first fluid drain path 5 isopen, allowing fluid from the first chamber 11 to drain through thefirst fluid drain path 5 to the sump 21. Again, motion of thereciprocating piston 1 assists this draining.

Optionally (not shown), the first fluid supply path 3 and first fluiddrain path 5 may pass through a single port in the housing 2. In thesame way, the second fluid supply 4 and drain 6 paths may also passthrough a single port.

Movement of the reciprocating piston 1 drives one or more poppet valves7 via a connector rod 9. One or more poppet valves 7 are connected tothe connector rod 9, the connection 8 being outside the housing 2.

As shown in FIGS. 2, 3, 5, 6 and 7 the connector rod 9 passes through anaperture 14 in the housing 2, the reciprocating piston 1 in co-operationwith an internal wall of the housing 2 forming a seal to preventsubstantial egress of fluid from the housing 2 through the aperture 14.Some small amount of fluid may egress under normal operation.

In the preferred embodiment of the invention shown, the seal provided bysaid reciprocating piston 1 in co-operation with said internal wall ofthe housing 2 is located adjacent said aperture 14 such that theaperture 14 is substantially sealed to prevent egress of fluid from thehousing 2 through said aperture 14. However, in an embodiment not shown,it is not necessary for the reciprocating piston 1 to abut the housing 2at aperture 14, but simply for the reciprocating piston 1 to abut thehousing 2 at locations which prevent fluid from the chambers 10 and 11from reaching the aperture 14. Hence, a reciprocating piston 1 may nothave a generally constant diameter as shown in the Figures, but mayinstead have a central portion of smaller diameter which forms a voidannulus with the housing 2. Alternately, in a less preferred embodiment,the reciprocating piston may seal only the chamber 10 or 11 containingpressurised fluid, there being no loss of pressure caused by failing toseal an empty chamber.

The overall internal friction of the valve operating apparatus isreduced, as the friction between the reciprocating piston 1 and housing2 will exist regardless of the location of an aperture 14 in the housing2. In prior arrangements, the reciprocating piston drives the poppetvalve by passing the poppet valve stem through an aperture at the baseof the lower fluid chamber. Accordingly, a high pressure seal capable ofsealing the hydraulic system at this point, under high operating speeds,is required. Achieving acceptable high speed operation is verydifficult, due to the large amount of additional internal friction sucha seal between the housing and poppet valve stem will create. Incontrast, the present invention eliminates the need for such a seal,greatly reducing the internal friction of the system and enabling thereciprocating piston 1 to be more easily reciprocated at high speed asnecessary, enhancing overall engine efficiency.

By using the reciprocating piston 1 in co-operation with an internalwall of the housing 2 to form a seal to prevent substantial egress offluid from the housing 2 through the aperture 14, there is minimalincrease in the friction already present and hence a significant overallimprovement compared to prior arrangements which include a seal aroundthe poppet valve stem. The present system is able to move thereciprocating piston more quickly, enabling greater precision ofcontrol. This ensures that the engine operates more efficiently.

Further, in an engine including a valve operating apparatus according tothe present invention, thermodynamic efficiency of the engine isimproved, as a throttle, which is inherently inefficient, is not neededto control the amount of air fed to the engine. Instead, the precisecontrol enabled due to the reduced internal friction enables variablecontrol of the reciprocating piston 1 and hence the poppet valves 7. Thevariable lift and variable timing of the poppet valves 7 controls theamount of air fed. Furthermore, the reduced internal friction enablesthe reciprocating piston 1 to be more easily reciprocated at high speedas necessary, further enhancing overall engine efficiency and providingcontrol over a greater range of operation.

The above described operation of the embodiment of the invention may bevaried due to the precise control available in the invention. Thereciprocating piston may be accelerated and decelerated by adjusting thetiming of opening and closing the fluid paths, and/or by partiallyopening fluid paths. The ability to decelerate the reciprocating pistonand thus the poppet valves ensures that crashing of the poppet valves onthe valve seats may be prevented.

Furthermore, because the connection 8 to the poppet valves 7 is madeexternally to the housing 2, it is possible to fit the apparatus to arange of existing automotive engines with minimal changes to thecylinder heads. This minimises the re-tooling required to convert anautomotive engine from a standard cam system, thereby reducing costs andmaking retrofitting of the apparatus more economical and easier toperform.

The connector rod 9 of the embodiment shown in the Figures is a straightrod, however a connector of other shapes, such as a U shape orasymmetric shape may be appropriate for particular engines, possiblyfurther reducing the changes required to be made to the cylinder heads.While the preferred embodiment has two diametrically opposed connectorrods 9, the end of each passing through diametrically opposed apertures14 in the housing 2, it is envisaged that a less preferred embodimentmay have a single connector rod 9 and single aperture 14.

In the preferred embodiment, the connection 8 between the connector rod9 and poppet valve 7 may allow each poppet valve 7 to spin naturallyabout their longitudinal axis. This is desirable as valve spin duringengine operation acts to reduce the build up of sediments on the valveand valve seats.

The apparatus may be mounted to the side of the one or more poppetvalves 7 rather than in-line, allowing multiple poppet valves 7 to beattached to a connector rod 9. Whilst potentially reducing the number ofvalve operating devices, a device according to the present inventionalso requires less height in the cylinder head than a device where thereciprocating piston 1 is in-line with the longitudinal axis of thepoppet valve 7 stern.

The opening and closing of the first and second fluid supply and drainpaths 3, 4, 5 and 6 is preferably performed by one or more fast actingcontrol valves. In one preferred embodiment, each fast acting controlvalve is a solenoid valve such as the example depicted in FIG. 4. Thefast acting control valve may also be a rotary valve or combinationvalve system. In another preferred embodiment, the control valves 24which open and close the respective fluid paths are a slide type.

The respective control valves may be located in the high pressurereservoir 22 or sump 21, or more preferably be respectively located inthe first or second fluid supply or drain paths 3, 4, 5 and 6. Bycontrolling the first and second fluid supply and drain paths 3, 4, 5and 6 open, partially open or closed, movement of the reciprocatingpiston 1 is controlled. In turn, through the connector rod 9, movementof the one or more poppet valves 7 is controlled.

In a preferred embodiment, the control valves 24 are controlled by anelectronic control device 19, which in turn is controlled by an EngineManagement System (EMS). In this respect, sensors would provideinformation to the electronic control device 19 or the EMS, includinginformation about the engine's speed, the driver's desired torque output(from an accelerator pedal sensor), the fluid temperatures andpressures, the valve positions, inlet air temperature, pressure andhumidity and inlet air mass flow metering. Sensors to provide suchinformation are generally used in modern Engine Management Systems.Information about the hydraulic system would also be detected, forexample, the hydraulic fluid pressure would be sensed by a sensor placedin connection with the fluid supply path(s). The electronic controldevice 19 or EMS would then use the information provided by sensors toadjust the poppet valve 7 lift and timing.

An apparatus according to the present invention allows for increasedengine efficiency, and control of the apparatus enables the lift andtiming of the poppet valves 7 to be controlled in a variable manner,responding to engine requirements. The precise control also allows thepoppet valve(s) 7 to be smoothly stopped without crashing onto therespective valve seat(s).

In a preferred embodiment, a positioning spring 12 returns thereciprocating piston 1 to a predetermined known position and thus theone or more poppet valves 7 to a predetermined known position when theengine is not in use. This has the advantage of further reducing thecomplexity of control components required, as it is not necessary todetermine the poppet valve 7 starting position when an engine isstarted. A benefit of having a positioning or return spring 12 is thatthe position at which the poppet valve 7 is held when the engine isinoperative is known and hence the position at start up is known. Thus,this approach represents a straightforward approach to determiningpoppet valve 7 position, further simplifying the apparatus and henceincreasing its reliability, and ease of manufacture. To ensure extrawork by the hydraulic system is not required to overcome such a spring12, the spring 12 could optionally be snibbed in place in a compressedstate by a catch 13 while the engine is in operation, only beingunsnibbed when the engine is inoperative, in order to bias thereciprocating piston 1 and poppet valve(s) 7 to a known position.

It will be recognised by those skilled in the art that the return spring12 could be located at various positions. For example, the return spring12 could be located at one end of the reciprocating piston 1, residingwithin the housing 2, as is shown in the embodiment of FIG. 5.Alternately, the return spring 12 could be mounted outside the housing2, for example on the poppet valve 7, as is shown in the embodiment ofFIG. 2, or be attached to the connector rod 9 (not shown).

A benefit of having a high pressure reservoir 22 of fluid is that theengine may be started without difficulty as there is no time delay tobuild up pressure, as may occur when a pump alone is used. Furthermore,any momentary interruption of supply from the pressure supply device 20may be compensated for by the high pressure reservoir 22. The reservoir22 may form a part of the hydraulic flow circuit as shown in FIG. 1, ormay not normally be a part of the flow circuit in usual operation, asshown in FIG. 1 a.

In a preferred embodiment, the reciprocating piston 1 may be formed withpartially hollow ends 18, as shown in the embodiment of FIG. 7. Holes inthe walls of the hollow ends allow the entry of fluid from respectivefluid supply paths into a chamber 10 or 11 formed between thereciprocating piston 1 and housing 2. Such an arrangement shouldsubstantially decrease the risk of the reciprocating piston 1 beingmomentarily jammed in the housing 2. However, the reciprocating pistonneed not be hollow, but of any geometry which presents a surface, which,in conjunction with the relevant chamber, allows the fluid to work uponthe reciprocating piston in the direction of its longitudinal axis, evenwhen the reciprocating piston is at full extension.

In a particularly preferred embodiment, the four fluid paths (first andsecond supply and drain paths 3, 4, 5 and 6) are individuallycontrolled, each path having its own control valve 24 which can becontrolled to be closed, partially open or open. Precise control of thereciprocating piston 1 is effected by the timing and condition of thecontrol valves. The reciprocating piston 1 first 16 and second ends 17have the same nominal surface area and the reciprocating piston 1 isdriven by pressurised fluid alternately supplied to each piston end 16and 17.

By opening control valve 24 located on the first fluid supply path 3,fluid is supplied to a first chamber 11 formed between a first end 16 ofthe reciprocating piston 1 and housing 2. The first fluid drain path 5connecting said first chamber 11 to a low pressure reservoir or sump 21is closed and the pressure thereby built up in the first chamber 11causes the reciprocating piston 1 to be hydraulically driven from afirst position to a second position. At the same time, the second fluidsupply path 4 may be closed and the second fluid drain path 6 open,allowing any fluid in the second chamber 10 to drain through the seconddrain path 6 to the sump 21. Motion of the reciprocating piston 1assists this draining.

Precise and variable control of the motion of the reciprocating piston 1may be obtained by varying operation of the control valves 24. Forexample, in order to decelerate the reciprocating piston 1, and hencethe poppet valves 7, the control valve 24 located on the second fluidsupply path 4 may be opened or partially opened before the reciprocatingpiston 1 has finished its motion. The pressure of the fluid supplied tothe second chamber 10 exerts a force against the motion of thereciprocating piston 1, decelerating it. The amount to which the valveis opened and the timing is controlled by the electronic control device19. A similar process may be followed for driving the reciprocatingpiston 1 in the opposite direction.

Importantly, in addition to being able to decelerate the reciprocatingpiston as desired, the distance traveled by the piston may be adjustedby the timing and amount of fluid supplied. For example, in order toshorten the distance traveled by the reciprocating piston 1, instead ofto decelerate the reciprocating piston 1, and hence the poppet valves 7,the control valve 24 located on the second fluid supply path 4 may befully opened before the reciprocating piston 1 has finished its motion,and the control valve 24 located on the first fluid supply path 3 may beclosed before the reciprocating piston 1 has finished its motion. Thepressure of the fluid supplied to the second chamber 10 exerts a forceagainst the motion of the reciprocating piston 1, stopping it.

When supplying fluid to the first chamber 11, the degree to which thecontrol valve 24 mounted in the fluid supply path 3 is opened willdetermine how quickly the chamber is filled and hence the speed at whichthe reciprocating piston 1 is driven.

Each of the four control valves 24 is independently operable, but isoperated in coordination with the other valves, an engine managementsystem controller 19 determining the degree to which the valve is openedand the timing of each valve in response to engine data.

The above abilities to directly control the speed, acceleration anddeceleration of the reciprocating piston, as well as the distancetraveled by the reciprocating piston 1, directly determine the timingand lift of the poppet valves 7, and hence the amount of air supplied tothe engine. As the control may be adjusted and varied constantly, and isvery responsive, the electronic control device can constantly adjust thelift and timing of the poppet valves, ensuring that an optimal airsupply is provided at all times. This ensures greater overall engineefficiency.

In less preferred embodiments, a reciprocating piston 1 having differentsurface area on each end may be used, and, for example, pressurisedfluid could be constantly supplied to one end. Furthermore, in otherless preferred embodiments, fluid at a lower pressure may be constantlysupplied to one piston end while pressurised fluid at a higher pressureis alternately supplied and drained from the second end. Theseembodiments may require a differing hydraulic system from that shown inthe Figures. These embodiments still retain the advantage of reducedinternal friction due to avoiding the need for a high pressure sealcapable of operating at high speeds around the poppet valve stem.

As the present invention may be embodied in several forms withoutdeparting from the spirit of the essential characteristics of theinvention, it should be understood that the above described embodimentsare not to limit the present invention, but rather should be construedbroadly within the spirit and scope of the present invention as definedin the appended claims. Various modifications and equivalentarrangements are intended to be included within the spirit and scope ofthe present invention.

1. A valve operating apparatus for an internal combustion engineincluding: a housing; a reciprocating piston residing wholly within thehousing, the reciprocating piston driving one or more poppet valves; afirst fluid supply path and a first fluid drain path, each path beingcontrollable to supply or drain fluid to/from a first reciprocatingpiston end; a second fluid supply path and a second fluid drain path,each path being controllable to supply or drain fluid to/from a secondreciprocating piston end; wherein said reciprocating piston, in use, isdriven between a first position and a second position by controllingsaid fluid in said supply and drain paths, thereby operating said one ormore poppet valves, and wherein a connector passes through an aperturein said housing to connect said reciprocating piston to said one or morepoppet valves, said reciprocating piston in co-operation with aninternal wall of the housing forming a seal to prevent substantialegress of fluid through said aperture from the first reciprocatingpiston end and from the second reciprocating piston end.
 2. A valveoperating apparatus according to claim 1 wherein said aperture issubstantially sealed by at least a portion of the external surface ofsaid reciprocating piston to prevent egress of fluid from the housingthrough said aperture.
 3. A valve operating apparatus according to claim1 wherein said aperture is located in a side wall of said housing, andwherein an external side wall surface of said piston in conjunction withan internal side wall surface of said housing forms said seal to preventsubstantial egress of fluid from the housing through said aperture.
 4. Avalve operating apparatus according to claim 1 wherein the longitudinalaxis of said connector is substantially perpendicular to thelongitudinal axis of said piston.
 5. A valve operating apparatusaccording to claim 1 wherein the connector is a rod fixed to thereciprocating piston and connects to said one or more poppet valves. 6.A valve operating apparatus according to claim 1 wherein said firstreciprocating piston end and said second reciprocating piston end havesubstantially the same surface area.
 7. A valve operating apparatusaccording to claim 1 wherein each of said first fluid supply path, firstfluid drain path, second fluid supply path and second fluid drain pathhas an independently operable control valve, said control valve operableto have a closed, partially open or open state, operation of the foursaid control valves regulating the flow of fluid to said first andsecond reciprocating piston ends, thus enabling control of the movementof the reciprocating piston and hence operation of the one or morepoppet valves.
 8. A valve operating apparatus according to claim 1wherein a reservoir of high pressure fluid is in fluid connection withone or more of said fluid supply paths.
 9. A valve operating apparatusaccording to claim 1 wherein fluid in said supply and drain paths iscontrolled by an engine management system controller, said enginemanagement system controller controlling the operation of thereciprocating piston and thus enabling variable lift and variable timingcontrol of said one or more poppet valves.
 10. A valve operatingapparatus according to claim 1 wherein said reciprocating piston may bedecelerated by controlling said fluid in said supply and drain paths toavoid crashing of said one or more poppet valves onto their respectiveseats.
 11. A valve operating apparatus according to claim 1 wherein saidreciprocating piston is biased when in an inoperative state to apredetermined position, thereby biasing each said poppet valve to apredetermined position and the biasing means being prevented from actingon the reciprocating piston when said reciprocating piston is in anoperative state.
 12. A valve operating apparatus according to claim 1wherein said reciprocating piston is partially hollow, said hollowproviding a surface upon which vertical force may act at least at oneend of said reciprocating piston.
 13. A valve operating apparatusaccording to claim 1 wherein said connector connecting the reciprocatingpiston to the one or more poppet valves allows each poppet valve to spinabout its longitudinal axis.
 14. An engine including a valve operatingapparatus according to claim
 1. 15. A motor vehicle including a valveoperating apparatus according to claim
 1. 16. A valve operatingapparatus according to claim 2 wherein: said aperture is located in aside wall of said housing, and wherein an external side wall surface ofsaid piston in conjunction with an internal side wall surface of saidhousing forms said seal to prevent substantial egress of fluid from thehousing through said aperture; and said connector is a rod fixed to thereciprocating piston and connects to said one or more poppet valves; andfluid in said supply and drain paths is controlled by an enginemanagement system controller, said engine management system controllercontrolling the operation of the reciprocating piston and thus enablingvariable lift and variable timing control of said one or more poppetvalves.
 17. A valve operating apparatus according to claim 16 whereinsaid reciprocating piston is partially hollow, said hollow providing asurface upon which vertical force may act at least at one end of saidreciprocating piston.
 18. A valve operating apparatus according to claim16 wherein each of said first fluid supply path, first fluid drain path,second fluid supply path and second fluid drain path has anindependently operable control valve, said control valve operable tohave a closed, partially open or open state, operation of the four saidcontrol valves regulating the flow of fluid to said first and secondreciprocating piston ends, thus enabling control of the movement of thereciprocating piston and hence operation of the one or more poppetvalves.
 19. A valve operating apparatus according to claim 18 whereinsaid reciprocating piston is partially hollow, said hollow providing asurface upon which vertical force may act at least at one end of saidreciprocating piston.
 20. A valve operating apparatus according to claim16 wherein said first reciprocating piston end and said secondreciprocating piston end have substantially the same surface area.
 21. Avalve operating apparatus according to claim 20 wherein saidreciprocating piston is partially hollow, said hollow providing asurface upon which vertical force may act at least at one end of saidreciprocating piston.
 22. A valve operating apparatus according to claim20 wherein each of said first fluid supply path, first fluid drain path,second fluid supply path and second fluid drain path has anindependently operable control valve, said control valve operable tohave a closed, partially open or open state, operation of the four saidcontrol valves regulating the flow of fluid to said first and secondreciprocating piston ends, thus enabling control of the movement of thereciprocating piston and hence operation of the one or more poppetvalves.
 23. A valve operating apparatus according to claim 22 whereinsaid reciprocating piston is partially hollow, said hollow providing asurface upon which vertical force may act at least at one end of saidreciprocating piston.
 24. A valve operating apparatus according to claim16 wherein said reciprocating piston may be decelerated by controllingsaid fluid in said supply and drain paths to avoid crashing of said oneor more poppet valves onto their respective seats.
 25. A valve operatingapparatus according to claim 24 wherein said reciprocating piston ispartially hollow, said hollow providing a surface upon which verticalforce may act at least at one end of said reciprocating piston.
 26. Avalve operating apparatus according to claim 24 wherein each of saidfirst fluid supply path, first fluid drain path, second fluid supplypath and second fluid drain path has an independently operable controlvalve, said control valve operable to have a closed, partially open oropen state, operation of the four said control valves regulating theflow of fluid to said first and second reciprocating piston ends, thusenabling control of the movement of the reciprocating piston and henceoperation of the one or more poppet valves.
 27. A valve operatingapparatus according to claim 26 wherein said reciprocating piston ispartially hollow, said hollow providing a surface upon which verticalforce may act at least at one end of said reciprocating piston.
 28. Avalve operating apparatus according to claim 24 wherein said firstreciprocating piston end and said second reciprocating piston end havesubstantially the same surface area.
 29. A valve operating apparatusaccording to claim 28 wherein said reciprocating piston is partiallyhollow, said hollow providing a surface upon which vertical force mayact at least at one end of said reciprocating piston.
 30. A valveoperating apparatus according to claim 28 wherein each of said firstfluid supply path, first fluid drain path, second fluid supply path andsecond fluid drain path has an independently operable control valve,said control valve operable to have a closed, partially open or openstate, operation of the four said control valves regulating the flow offluid to said first and second reciprocating piston ends, thus enablingcontrol of the movement of the reciprocating piston and hence operationof the one or more poppet valves.
 31. A valve operating apparatusaccording to claim 30 wherein said reciprocating piston is partiallyhollow, said hollow providing a surface upon which vertical force mayact at least at one end of said reciprocating piston.